BOSTON – Attorneys for Boston crime boss James “Whitey” Bulger filed an appeal Thursday of the federal convictions that sent him to prison for life last year, arguing that he was not given a chance to fully present his defense as he stood trial for 11 killings and other gangland crimes dating to the 1970s and ’80s.

Bulger’s lawyers said the former head of Boston’s Irish mob, now 84 years old, had not been allowed to argue that Jeremiah O’Sullivan, a now-deceased federal prosecutor, had given him immunity.

Bulger had been an FBI informant against the rival New England Mafia, and his case became a black eye for the FBI after it was revealed that corrupt agents had accepted bribes and protected him over the years.

But, during the trial last year, Judge Denise Casper disallowed the immunity claim, saying that O’Sullivan had no authority to grant such immunity.

Bulger was a fugitive for 16 years until his 2011 arrest in California.

He was convicted of federal racketeering, including money laundering and playing a role in 11 murders, as well as firearms violations, following a 35-day trial. In November, he was sentenced to life in prison.

Bulger’s appeal was filed the appeal late Thursday in the 1st U.S. Circuit Court of Appeals in Boston.